1. Field of the Invention
The present invention relates to a micromechanical moisture sensor device, a corresponding manufacturing method, and a micromechanical sensor system.
2. Description of the Related Art
The present invention and the underlying problem are explained based on silicon-based micromechanical moisture sensors and pressure sensors, although they are in principle applicable to any micromechanical moisture sensor devices.
Micromechanical pressure sensors have become standard sensors in both the automotive field and the consumer application field. Moisture sensors are currently gaining importance for ascertaining the additional measured variable of moisture.
At the present time, both sensor types are available as single sensors in a micromechanical design and are applied in stand-alone packages. Each sensor has the same access to the media surroundings and thus sees the same surrounding conditions. However, it is in principle also conceivable to integrate both sensor types in the same substrate, as explained below based on FIG. 6.
FIG. 6 is a schematic cross-sectional representation of a micromechanical moisture sensor device known from published German patent application document DE 199 17 717 A1 in combination with a pressure sensor device known from published German patent application document DE 198 53 135 A1.
In FIG. 6, reference numeral 1 refers to a silicon substrate having a front side V and a rear side R, in which a moisture sensor FS0 and a pressure sensor PS are integrated side by side.
Moisture sensor FS0 has a potential well 5, for example, a p-well, situated in the substrate. An insulating layer 4, for example, made of silicon nitride, is applied on front side V of substrate 1. An interdigital printed conductor track arrangement including printed conductor track sections L1, L2, and L3 is applied above potential well 5 and on insulating layer 4, on which a moisture-sensitive polymer layer 10 is situated, which extends into the gaps between the printed conductor track sections L1, L2, L3 and thus surrounds them. Not shown in FIG. 6 is an optional electrode, for example, a gold electrode, which is provided on moisture-sensitive polymer layer 10.
Using a capacitance measurement, it is possible to determine the moisture content of moisture-sensitive polymer layer 10, for example, via a simple capacitance measurement, a half-bridge measurement, or a full-bridge measurement, in which in the latter measurement, multiple interdigital printed conductor track arrangements would have to be provided side by side on insulating layer 4.
Pressure sensor PS according to FIG. 6 has a cavern 3 situated in substrate 1, above which a diaphragm area M is formed. Piezoresistive resistors P1, P2 are provided in or on diaphragm area M, which change their resistance under deformation of diaphragm area M and thus are able to provide a signal for ascertaining the applied pressure.